Enables event resizing via drag handles

Adds a resize handle manager to handle mouse hover
effects on calendar events and display a resize indicator.

This allows users to visually identify and initiate
event resizing by hovering near the bottom edge of an event.

src/managers/ResizeHandleManager.ts

@@ -0,0 +1,89 @@
+export class ResizeHandleManager {
+  private resizeZoneHeight =15; // Must match CSS ::after height
+  private lastHoveredEvent: HTMLElement | null = null;
+
+  public initialize(): void {
+    this.setupEventListeners();
+  }
+
+  private setupEventListeners(): void {
+
+    // Listen to global mouseover from document
+    document.addEventListener('mouseover', (e: MouseEvent) => {
+      this.handleGlobalMouseOver(e);
+    });
+
+    document.addEventListener('mousemove', (e: MouseEvent) => {
+      this.handleGlobalMouseMove(e);
+    });
+
+    document.addEventListener('mouseout', (e: MouseEvent) => {
+      this.handleGlobalMouseOut(e);
+    });
+  }
+
+  private handleGlobalMouseOver(e: MouseEvent): void {
+    const target = e.target as HTMLElement;
+    const eventElement = target.closest<HTMLElement>('swp-day-columns swp-event');
+
+    if (eventElement) {
+      this.lastHoveredEvent = eventElement;
+    }
+  }
+
+  private handleGlobalMouseMove(e: MouseEvent): void {
+    // Check all events to see if mouse is in their resize zone
+    const events = document.querySelectorAll<HTMLElement>('swp-day-columns swp-event');
+
+    events.forEach(eventElement => {
+      const rect = eventElement.getBoundingClientRect();
+      const mouseY = e.clientY;
+      const mouseX = e.clientX;
+
+      // Check if mouse is within element bounds horizontally
+      const isInHorizontalBounds = mouseX >= rect.left && mouseX <= rect.right;
+
+      // Check if mouse is in bottom 25px of the element
+      const distanceFromBottom = rect.bottom - mouseY;
+      const isInResizeZone = distanceFromBottom >= 0 && distanceFromBottom <= this.resizeZoneHeight;
+
+      if (isInHorizontalBounds && isInResizeZone) {
+        this.showResizeIndicator(eventElement);
+        console.log('✅ In resize zone - bottom 25px');
+      } else {
+        this.hideResizeIndicator(eventElement);
+      }
+    });
+  }
+
+  private showResizeIndicator(eventElement: HTMLElement): void {
+    // Check if indicator already exists
+    let indicator = eventElement.querySelector<HTMLElement>('swp-resize-indicator');
+
+    if (!indicator) {
+      indicator = document.createElement('swp-resize-indicator');
+      eventElement.appendChild(indicator);
+    }
+
+    eventElement.setAttribute('data-resize-hover', 'true');
+  }
+
+  private hideResizeIndicator(eventElement: HTMLElement): void {
+    const indicator = eventElement.querySelector<HTMLElement>('swp-resize-indicator');
+    if (indicator) {
+      indicator.remove();
+    }
+    eventElement.removeAttribute('data-resize-hover');
+  }
+
+  private handleGlobalMouseOut(e: MouseEvent): void {
+    const target = e.target as HTMLElement;
+    const eventElement = target.closest<HTMLElement>('swp-day-columns swp-event');
+
+    if (eventElement) {
+      // Don't remove immediately - let mousemove handle it
+    }
+  }
+
+  
+}